1. Field of the Invention
The present invention relates to a dual-mode regulator circuit, more particularly to a dual-mode regulator circuit capable of quickly determining the type of connected external circuit according to a voltage at an output terminal of the dual-mode regulator circuit, and then switching between a linear regulator mode and a switching regulator mode according to the determination made.
2. Description of the Related Art
In recent years, in order to meet the demand for low static power, conventional linear regulators used in microcontroller units (MCUs), or other similar systems on a chip (SOCs) and embedded systems are gradually being replaced by switching regulators.
The switching regulator is far more efficient than the linear regulator. For example, when used in a power system with 3.3V input voltage and 1.2V output voltage, the switching regulator can achieve a power conversion efficiency higher than 80%. In contrast, the linear regulator has a maximum efficiency of only 36%, which gives an efficiency difference between the two kinds of regulator of more than 44%.
While the switching regulator has a significant advantage with its high efficiency, it also has certain drawbacks. The switching regulator functions by continuously switching the power component on and off during operation, resulting in the voltage level of a node in the circuit to continuously switch between 0 volts and the voltage of the power source, and therefore a large current passes through the node. So, due to the rapid switching of the voltage level, significant bouncing may occur at the node. Another problem is that the switching regulator may interfere with other circuits through electromagnetic interference (EMI), and so electromagnetic compatibility (EMC) might have to be addressed.
Nowadays, more and more MCUs have switching regulators and linear regulators integrated on the same chip, so that the user can decide which regulator to use. Nevertheless, when powering-on, the system may fail to decide whether the connected external circuit is suitable for the switching-type or the linear-type regulator.